Engine exhaust systems have utilized hydrocarbon retaining devices, such as hydrocarbon traps, to retain cold start emissions for later reaction, or to recirculate into the engine intake system. In one particular example, the purging of exhaust gases may be enabled when the device reaches a predetermined temperature.
However, the inventors herein have recognized several issues with such examples. For example, desorption of the stored hydrocarbons may occur over a significantly long duration under some conditions. As such, if the engine is stopped before the stored hydrocarbons are sufficiently purged, subsequent cold start emissions may increase. Further, extended purging operation may limit other operations, such as adaptive fuel learning, etc.
In one approach, the above issues may be addressed by a system for managing emissions of an engine of a vehicle, the system comprising: a first exhaust passage including an emission control device, the first passage including a downstream section, the downstream section downstream of the emission control device and including a tailpipe of the vehicle; and a second exhaust passage coupled to the first exhaust passage downstream of the emission control device, the second exhaust passage including a hydrocarbon retaining system, the hydrocarbon retaining system including a vent passage, where at least a portion of the vent passage is positioned adjacent and thermally coupled to at least a portion of the downstream section of the first exhaust passage.
In this way, it is possible to utilize waste exhaust heat to improve purging of the hydrocarbon retaining system to the engine intake. This can be especially advantageous in that when the exhaust gas is warm enough to provide sufficient heat to the vent passage, an emission control device it also sufficiently warm enough so that purging operation can be carried out.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.